Pain in lower abdomen but not UTI?

[Satori86]

My problems began on the 14th February when I was rushed into hospital with a perianal abscess. It was operated on and removed and they left a vessel loop drain in for 2 weeks. They gave me 1 week of pain killers and laxatives to take.

During this time I started to have pain when I urinated so went to the doctor and was confirmed to have a UTI. I was given antibiotics for 5 days which I took and finished the course and symptoms left.

4 days later I went to the hospital had the loop removed and they confirmed the wounds from my surgery were healing well.
A few days later I was back at the doctors with discomfort and they confirmed another UTI. They explained that during surgery they had used a catheter. I got more antibiotics for 7 days and again finished the course.

On the second to last day of taking my antibiotic I began to get pain in my lower abdomen and also in my back which seemed similar to when the UTI was present.
I went back to my doctor and gave a urine sample but the test came back negative.

For the past 4 days I have been in quite extreme pain and discomfort with abdomen pain and pressure. I also get pain when I stop urination but not during.
I thought perhaps I had trapped air in my intestines as the pain is somewhat similar but it has not gone after 5 days.
I stopped all medication 3 days ago laxatives included when the pain was strong.

Has anyone has a similar experience or have any advice please. It's been the worst pain of my life so far.